Audio playback devices become more and more important. Particularly, an increasing number of users buy home-cinema entertainment equipment and other audio surround systems.
In home-cinema movies, very low frequencies are not exceptional. Frequencies of 30 Hz and lower are for instance typical for effects like earthquakes, running dinosaurs, explosions, etc. Audio data in the low frequency range may therefore contribute significantly to the movie experience.
On the other hand, speaker systems designed for low frequency reproduction, for instance a vented subwoofer, may not have the ability to reproduce these low frequencies with sufficient accuracy.
In order to create the “sensation” of perceiving lower frequencies than the loudspeaker can really reproduce, psycho acoustic effects such as the effect of the “missing fundamental” can be exploited. However, algorithms using the principle of the missing fundamental have not yet found their way into home-cinema applications.
BaryBass is an audio concept, which assumes a system with satellites and a subwoofer. A feature of BaryBass is to create a bass impression by projecting the band (or a part of it) that the satellites cannot reproduce to one single frequency. This frequency is amplified and reproduced on a closed loudspeaker box containing a sufficiently high quality loudspeaker. In this way, it may be possible to obtain a high efficient subwoofer. To give an example, with satellites having a cut-off frequency at 120 Hz, ultimately the frequency band between 20 Hz and 120 Hz is projected to one frequency. If that frequency is too low, for instance 50 Hz, the gap between the satellites and the single tone becomes obvious. If the frequency is chosen too high, for instance 70 Hz, the tone becomes noticeably un-harmonic to the rest of the music.
Other systems may work well on full range loudspeakers without the existence of satellites. For instance, a vented system may be provided having a purpose to reproduce a band of frequencies that a subwoofer cannot reproduce as such. A purpose may be not to make a smaller, more efficient subwoofer, but to make more frequencies audible than the subwoofer can physically reproduce. It does not introduce an extra gap between possible satellites and the subwoofer. In a home-cinema application, a subwoofer box may be tuned at a rather low frequency (for instance 50 Hz) where the un-harmonicity is less a problem.
Coming back to BaryBass, this technology may project a frequency range to one single constant frequency. It is also possible to project a frequency range to a slightly varying frequency.
WO 2005/027569 A1 discloses a device for producing a driving signal for a transducer, such as a loudspeaker. The driving signal has a frequency substantially equal to a resonance frequency of the transducer and an amplitude controlled by an external signal. The device is arranged for automatically adjusting the frequency of the driving signal to the resonance frequency of the transducer, using a control path. The device may be part of a frequency adaptation device for adapting a frequency range of an audio signal to the transducer.
However, conventional audio systems may suffer from a non-sufficient sound quality, particularly in the bass frequency range.